The present invention relates to a dry etching method in which plasma is used and, in particular, to an etching method for a three-dimensional structure device.
Recently, along with a high integration of a flash memory, a three-dimensional memory structure in which a channel or a gate electrode of each storage device is laminated in the vertical direction is studied. For realizing such a three-dimensional memory structure, an etching technology in which a Poly-Si film and an SiO2 film, or an SiN film and an SiO2 film are set to a pair layer and a via or a trench having a high aspect ratio can be consistently processed to a plurality of pair layers is required.
For example, JP-A-2013-80909 discloses that an amorphous carbon layer (ACL; hereinafter, referred to as an ACL) is set to a mask film, and when a high aspect laminated structure having a pair layer of a Poly-Si film and an SiO2 film is dry etched, a mixed gas containing an NF3 gas and a CH2F2 gas is used. Further, JP-A-2013-80909 discloses a technology in which in a main etching process, a via is etched to a taper shape by a gas system and an over etching process in which pressure is dropped is continuously applied, and thereby a bottom part having the taper shape is widened and a via having a high aspect ratio is vertically etched.